docs: def remove_variable(self, name):
          """Remove a variable from the problem."""
          index = self._get_var_index(name)
          # Remove from matrix
          self._A = np.delete(self.A, index, 1)
          # Remove from bounds
          del self.bounds[name]
          # Remove from var list
          del self._variables[name]
          self._update_variable_indices()
          self._reset_solution()